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Distributor Diagnosis


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People are telling me that mine maybe bad n a different thread. My issue was truck started running rough. Didn't have the power it did just a general running poorly. I adjusted timing got slightly better. Then one day on interstate i had gotten on it and it died. Hasn't started since. I thought it was crank sensor. But I've checked everything n the world I can think of. Supposedly it can still spin and be bad bearings. Idk. I've never heard of that

 

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I haven't had one fail on me yet, but from what I've read, the classic failure mode of the VG dizzy is that it usually works when it's cold, then starts running like crap as it warms up. Some people report finding red dust inside the dizzy at the same time, likely from the dizzy bearings starting to go. The check I've read for the bearings is to take the dizzy out (make sure you know which way it was pointing so you know how to put it back), spin it by hand, and see if it suddenly stops spinning like it's catching on something.

 

IIRC someone had the screw that holds the rotor on fall off and bounce around inside, but that should be fairly obvious once the cap is off. Sounds like the cap/rotor have to be pretty knackered before you notice any issues there. One or two guys have reported the engine trying to idle counterclockwise after they've shut it off, and IIRC at least one of them said a new dizzy stopped it--I doubt that's a common fault though.

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Currently has a small miss at idle, then if racing the engine it'll seem to cut out and drop about 2-300 rpm and then pick up. Almost like it's hitting a rev limiter, but slower and more intermittent.

 

MAF checked out within spec, as did both injectors. No codes. Cleaned out the idle solenoids, looked clean but sprayed them out anyway. EGR didn't seem to be stuck.

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I had a distributor that would act up between 2500-3000 rpm. It would miss in that rpm range. Driving down the highway in that range was very annoying. I had no cel either.

 

The sensor is built into the distributor which sucks.

 

Lift up on the egr valve while the truck is running. If it stumbles, the egr is working. I'm not saying the pathway isn't somewhat clogged, simple test for the egr.

Edited by RF600
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Got my hands on an oscilloscope today, TPS checked out perfectly, no dead spots, hooked up to crank signal, got a couple of funky waveforms intermittently that matched up with my stumble. Also was getting wandering in the primary coil waveform.

Edited by PathyAndTheJets
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I bit the bullet and bought a new one. 165 bucks. Got it in and the timing set. Definitely idles smoother. Haven't had a chance to take it for a spin.

 

Iirc the MPFI dizzy is different than the TBI. The offer is much appreciated.

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